The invention is based on a heat exchanger according to the preamble of claim 1.
The specific contamination of the environment resulting from the emission of carbon dioxide by internal combustion engines is primarily a factor of their efficiency. This is not satisfactory, among other things, when the internal combustion engine is operated below its optimal operating temperature. In a few operating conditions, such as during cold starting or long downhill driving of motor vehicles, the optimal temperature of the internal combustion engine is not reached, which leads to increased fuel consumption and increased exhaust-gas emissions. During cold starting at low outside temperatures, heat is also needed to deice the windows or to warm the passenger compartment of the vehicle, in order to improve driving safety and comfort. Currently, chemical or electrical supplementary heating systems are used in particular to solve this problem. Their use also results in increased fuel consumption, however.
A heat exchanger was made known in a supplement entitled “System Partners 98”, page 4 of the MTZ (Motor Technische Zeitschrift) Jul. 2, 1998 that is installed in an exhaust-gas return line in order to cool the exhaust gas to be returned to a combustion chamber of the internal combustion engine. Cooling the exhaust gas improves the aspiration. Since the heat exchanger is used constantly during the entire operation of the internal combustion engine, heat is continuously absorbed by the coolant of the internal combustion engine, even during full-load operation. In order to prevent overheating of the coolant and the internal combustion engine in this driving state, however, heat must also be dissipated by way of the main radiator of the internal combustion engine. The main radiator and the cooling fans assigned to it must be designed accordingly to be larger in size.